BenSound.com is a nice site which offers Royalty Free Music. The only caveat is that you have to give credit to BenSound. Here’s what the site says.

“My music is licensed under a Creative Commons License:
You are free to use the music in your multimedia project (online videos(youtube,…), websites, animations, etc.) as long as you credit me, For example: “Music: www.bensound.com” or “Royalty Free Music from Bensound”